Effect of Bi2O3 addition on the microstructure and electrical properties of lead-free (Na_(0.5)K_(0.5))NbO3- Bi(Na_(0.80)K_(0.20))TiO3 ceramics

摘要

Although PbZrO3-PbTiO3 (PZT)-based ceramics are playing a dominant role in piezoelectric materials, their evaporation of harmful lead oxide during the sintering process causes a crucial environment problem. It is necessary to search for lead-free piezoelectric materials that have such excellent properties as those found in the PZT-based ceramics. Therefore (Na_(0.5)K_(0.5))NbO3-based solid solutions were studied to improve piezoelectric properties. In the present study, various quantities of Bi2O3 were added into 0.98(Na_(0.5)K_(0.5))NbO3-0.02Bi(Na_(0.80)K_(0.20))TiO3 (0.98NKN-0.02BNKT) ceramics. It was found that 0.98NKN-0.02BNKT with the addition of 0 ~ 0.5 wt.% Bi2O3 exhibit relatively good piezoelectric properties. For 0.98NKN-0.02BNKT ceramics, the electromechanical coupling coefficients of the planar mode k_p and the thickness mode k_t reach 0.35 and 0.41, respectively, at the sintering of 1100 °C for 3 hrs. For 0.98NKN-0.02BNKT ceramics with the addition of 0.3 wt.% Bi2O3, the electromechanical coupling coefficients of the planar mode k_P and the thickness mode k_t reach 0.42 and 0.46, respectively, at the sintering of 1100 °C for 3 hrs. It is obvious that 0.98NKN-0.02BNKT solid solution ceramic by adding low quantities of Bi2O3 is one of the promising lead-free ceramics for electromechanical transducer applications.